The objective of this research is to uncover the neural correlates of several binaural phenomena in audition. These phenomena are: lateralization, masking, and masking level difference. Lateralization refers to the spatial aspects of a sound entering the two ears; masking is concerned with the obscuring of one sound by another; and masking level difference refers to the increase in detectability in certain binaural conditions over other binaural and monaural conditions. This research will be concerned with the single neuronal responses of the medial superior olivary nucleus and the inferior colliculus of kangaroo rat to acoustic stimuli. The neural responses to auditory stimulation will be stored in and analyzed by a digital computer. Interval, period, and post-stimulus- time histograms will be the usual ways of data acquisition and the statistics appropriate for such distributions will be used in the analyses of the data. The location of all the neurons studied will be histologically verified so that the functional role of brain-stem nuclei in binaural hearing can be understood.